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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

FXUS66 KSGX 132126

Area Forecast Discussion
National Weather Service San Diego CA
126 PM PST Thu Dec 13 2018

The offshore flow will weaken tomorrow, allowing the sea breeze to 
bring cooling west of the mountains. More high clouds will dim the 
sun at times as well. Little change this weekend as a weak trough 
moves inland. There is a small chance for some light precipitation 
later Monday, then dry and warmer into midweek as high pressure 
builds aloft and gusty winds turn back offshore. A high surf event 
is expected early next week as well.



Skies were clear over SoCal early this afternoon. The sfc pressure 
gradient from SW NV to KSAN was near 8 MBS. This was supporting NE 
winds 20 MPH with gusts to around 30 MPH along the coastal foothills 
and through the passes. 

High pressure aloft will weaken a bit over SoCal this weekend as a 
weak trough moves through it. More high clouds will arrive as well, 
dimming the weak December sun for slightly cooler weather.

Another short-wave trough will slide down the ridge early next week, 
building sfc high pressure over the Great Basin and forcing gusty 
offshore flow across SoCal during the midweek period. The offshore 
flow and building heights/thickness will bring dry and warmer days 
with above average temperatures once again. both the 12Z GFS/ECMWF 
runs have the peak of the ridge over us by Thursday of next week, 
weakening into the following weekend.

Low POPS are still in the forecast around the late Mon period as the 
shortwave draws stronger onshore flow and deepens the marine layer, 
If any precip does manage to develop, it will be very light and west 
of the mts. The main story will be high pressure holding aloft for 
the next seven to ten days. 


132130Z...Clear skies with unrestricted vis will prevail through 
Friday. Areas of NE-E surface wind gusts of 15-30 kt will continue 
through Friday morning mainly below mountain passes and near the 


No hazardous marine weather is expected through Sunday. A large WNW 
swell Monday and Tuesday will likely generate seas of 10-13 feet, 
highest in the outer coastal waters (beyond 30 nm), though the 
period will be quite long, 18-20 seconds.


A large long-period (18-20 seconds) swell from the west-northwest is 
currently projected to arrive Monday and continue through Tuesday. 
The direction from 290 degrees will limit the effects somewhat, 
though surf of 6-12 feet, locally higher, is still quite possible, 
especially in southern San Diego County. Stay tuned in coming days 
to any hazard products as the swell approaches.


Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.